I think we will see:
1) Considerable revisions to Finder
Justification:
- It needs it as it has been neglected for too long and there are some obvious flaws/bugs/performance issues, or is the case of networking, read all of the above.
- Apple have not changed much in the Finder in the developer seeds (from what I have seen in the screenshots), which makes me suspicious something is coming. Expect it to make use of Core Animation, for example, when you sort a folder by name the icons will move places using a swish animation, rather than jumping from one static state to another.
2) Apple will take the wraps of new GUI to once again take Macintosh computing to the cutting edge (and coincidentally make Windows Aero look second rate)
Justification:
- This look has graced the Mac for 7 years, so I think Apple will look to push things forward.
- Aqua was developed in 18 months, which is > the time between 10.4 and 10.5, so it is certainly possible.
- The shiny/aqua look went away from Apple's hardware a long time ago.
- Yes, I know apps will have to be changed, especially if the use custom widgets, but this will be possible in the time between receiving the beta (early June) and the product shipping (sometime in October).
3) Possible: .Mac improvements and integration with either current Google services or something Apple and Google have been collaborating on. Developers will need to know about this because some of their Apps integrate with .Mac. And some of them may be .Mac customers.
4) Possible: Previews of iLife and iWork Leopard Editions. Although an audience of developers may not be too interested in what are essentially consumer apps. That said Apple may want to showcase these to inspire developers to show what they can do with the new technologies in Leopard.
5) Definite: A dig at Vista, somewhere, from someone.